This invention relates to a surgical stapler apparatus, and more particularly to a surgical stapler apparatus having a transversely flexible shaft intermediate the portion of the apparatus which performs the stapling (hereinafter the "applicator portion") and the actuator portion of the apparatus. (For simplicity, discussion hereinafter will largely be confined, in terms, to surgical staplers, but it is to be understood that the scope of the invention includes apparatus for applying any type of surgical fasteners.)
There are several known types of surgical staplers in which the stapling takes place at a location relatively remote from the location at which the stapler is held and actuated by the operator. Examples of such staplers are the linear closure surgical staplers shown in U.S. Pat. No. 3,494,533, issued Feb. 10, 1970, to Green et al., and commonly assigned herewith, and the circular anastomosis surgical staplers shown in U.S. Pat. No. 4,304,236, issued Dec. 8, 1981, to Conta et al., and commonly assigned herewith. Typically, in instruments of the types shown in these patents, tissue to be stapled is clamped between an anvil assembly and a staple holding assembly, both of which are located at the distal end of the instrument. The clamped tissue is stapled by driving one or more staples from the staple holding assembly so that the ends of the staples pass through the tissue and are clinched by being driven against the anvil assembly. The forces required to operate the instrument are applied by the operator of the instrument to an actuator mechanism located at or near the proximal end of the instrument. The applicator and actuator portions of the instrument are joined by a longitudinal connecting shaft along which the actuating forces are transmitted to the distal applicator. This type of construction, including relatively widely spaced distal and proximal portions, may be employed for any of several reasons, such as the relative inaccessibility of the tissue to be stapled, or the need to see the tissue well during stapling.
In some applications of instruments of the types mentioned above, it may be desirable for the longitudinal shaft joining the distal and proximal portions of the apparatus to have at least a section that can be bent in a direction transverse to the longitudinal axis of the instrument. This may facilitate placing the instrument in particular body structures or reaching remote or relatively inaccessible stapling sites, or it may allow the staples to be applied at various angles relative to the actuator portion of the instrument.
The approach taken in the present invention is to transmit only a small force hydraulically along the flexible shaft and to use that force to generate a larger force in the applicator to apply the staples to the tissue. By localizing the large stapling force in one end of the apparatus, and making the force transmitted along the flexible shaft sufficiently small, the flexible shaft can be kept from straightening significantly during application of the staples.
In instruments employing anvils against which the fasteners are clinched, the tissue is typically clampled between the anvil and a cooperating portion of the instrument with a force determined by the tissue thickness and by the gaps between the anvil and the cooperating element. It is desirable to be able to control the pressure on the tissue by adjusting the gap. In one known device, disclosed in U.S. Pat. No. 3,638,652, issued Feb. 1, 1970, to Kelley, the tissue to be stapled is held between the staple-holding unit and the clincher, and the staples are applied by means of pulling the staple holder toward the anvil. The pressure on the tissue at each instant depends almost entirely on the force exerted on the tissue by the staples. It is desirable, however, to control the clamping pressure entirely independently of the fastener application process.